"At this time, a 5/7 (May 7) launch is unlikely," SpaceX announced through its twitter account. "We will issue a statement as soon as a new launch target is set."

SpaceX was aiming for a Monday liftoff of its Falcon rocket and Dragon capsule. Issues with the software responsible for controlling the automated spacecraft are assumed to be responsible for the latest delay.

The earliest possible launch date would be next Thursday. Otherwise, SpaceX will need to wait until the Russians send a new crew to the space station on May 15.

SpaceX aims to be the first private company to send its own spacecraft to the space station on a cargo mission. NASA used to stockpile the space station through the space shuttles, but the fleet was retired last summer. The space agency wants commercial providers to take over that role.